The present invention relates to an opto-electronic indicating matrix with row and column segments which are controlled in multiplex operation. The present invention also relates to an indicating device which uses the inventive opto-electronic indicating matrix.
The opto-electronic structural elements are active or passive structural elements which send light signals. The active structural elements are semiconductor emitters such as light-emitting diodes (LED), semiconductor indicators and gas-discharge indicators. Passive structural elements are especially liquid crystal indicators, in which the surrounding air is modulated and so that the required contrast change is achieved.
Matrices are composed of individual segments which are arranged in n rows and m columns. For example in the case of seven segment indicator, seven LED are mounted on a metal support and cast with synthetic plastic material Numerical or alphanumerical indicators can be designed both for static and also so-called time multiplex operations with frequencies which lie for example over 25 Hz, to provide a flicker-free representation.
The liquid crystal indicators are of a growing importance. Liquid crystals are mainly organic compounds which in liquid crystal condition, depending on the surrounding temperature, assume an anisotropic or isotropic phase. In the anisotropic or also meso phase the liquid crystal displays certain crystalline properties, such as for example, the double refraction which can be used for the indicating purpose. In liquid crystals one distinguishes nematic, cholesteric and smectic liquid crystals, depending on the type of the principle of the effective order., For conventional liquid crystal indicators, nematic liquid crystals are utilized. The liquid crystal indicators are composed of one or several cells, each including two glass plates arranged parallel to one another at a distance of approximately 10 .mu.m. Their inner surfaces are coated with transparent electrode layers which are etched in correspondence with the desired indicator configuration. A nematic liquid crystal is located between the glass plates. The cell is hermetically closed from outside.
Liquid crystal indicators are characterized especially by the low power consumption. Because of their low voltage consumption they can be operated with integrated switching circuits. In the simplest type of control for liquid crystal indicators, all elements or segments of the indicator are controlled in parallel operation. It is, however, possible to connect the same segments of different elements with a control conduit and thereby to reduce the number of the connecting conduits. This type of control is identified as multiplex operation. However, the produced contrast, the angular dependency of the contrast and the angular region are strongly dependent on the multiplex rate of the indicator. The lower is the multiplex ratio, the better is the whole contrast, the lower is the angular dependency and the lower is the angular region of the contrast. Thereby generally the multiplex ratio must be selected as low as possible.
A problem, with the multiplex operation of opto-electronic indicating matrices is the guidance of the conductor connectors. It has been proposed to control the matrix cells lying inside the indicating region by means of the through-contacting points from the rear side of the display, which however is technologically very expensive. Further, it has been proposed to perform the control through thin ducts between the matrix points. In this solution, however, each segment of one cell must be laterally offset relative to the segment of a neighboring cell, so as to produce nonrectilinear columns. As a result, the appearance of the matrix display produces an inhomogeneous impression with zigzag-shaped or inclined symbols.